stevenson



Jan. 31, 1956 A. B. STEVENSON STRING Filed Jan. 26, 1953 FIG. 2.

INVENTOR ALLAN B. STEVE NSON ATTORNEY United States Patent STRING Allan B. Stevenson, Attleboro, Mass, assignor, by mesne assignments, to American Sisalkraft Corporation, a corporation of Delaware Application January 26, 1953, Serial No. 333,240

1 Claim. (Cl. 154-535) This invention relates to an improved string adapted for wrapping and packaging and particularly to a string of substantial tensile strength formed of fiber which may be either continuous filaments or staple length strands such as waste scrap staple assembled into string and united with adhesive, without the need for the usual spinning or twisting operations.

In accordance with the present invention, the continuous filaments or staple strands are formed into string by bonding the fibers, of whichever type, into a unitary string with adhesive which impregnates the fibers to substantial saturation.

The string has strength in tension comparable to or greater than that obtainable by twisting or spinning of staple length strands as in conventional manufacture. The adhesive with which the fibers are impregnated is especially effective in the use of the string in wrapping and packaging, by enabling the string to be secured about a package adhesively, so that it is not necessary to secure the string by tying.

The string is adapted to be secured adhesively in several ways depending upon the type of adhesive employed. Thus, where the adhesive is of a permanently sticky pressure-sensitive type, the string is readily fastened about a package by merely twisting or rolling the ends of the string together. Where a certain amount of pressure may readily be applied to the body of the string about the package, whether the packaging is accomplished manually or by machinery, the ends of the string need not be twisted or rolled, but the package may be secured merely by pressing the tacky string against the package.

The adhesive may also be of a thermoplastic type and used in the same way except that the latent tackiness is developed by the application of heat.

A solvent plastic adhesive also may be employed in substantially the same way except that the string is moistened either along its entire body or merely at its end to develop the latent tackiness by a solvent so that the string is secured about the package upon evaporation of the solvent.

The permanently tacky, pressure-sensitive adhesive is, of course, permanently flexible since it is plasticized to the point of permanent tackiness. The other dry types of adhesive, thermoplastic and solvent plastic, when used, are plasticized sufliciently for optimum flexibility in use in packaging about small diameter articles, as Well as around sharp corners, without cracking the adhesive.

The present invention utilizes various fiber materials such as natural or synthetic fiber, but is outstanding for its utility in the conversion of glass fiber to a useful string. Glass fiber can not effectively be knotted because of its extreme weakness in shear. This inherent weakness of glass fiber has rendered it virtually useless for string and one object of the present invention is to obviate this problem and by so doing to provide a glass fiber string which takes advantage of the exceptional strength in tension of glass fibers.

The shape of the string in cross section may be round, flat, oval, rectangular, triangular, or otherwise because, as will appear, the present invention affords a wide selection in that respect.

In the drawing:

Fig. l is a diagrammatic perspective view illustrating a preferred way of manufacturing the binding string of the present invention;

Fig. 2 shows a package secured with the string.

Referring to Fig. 1, the numeral 10 designates a tank containing an adhesive 12 of a type to be referred to. Mounted on shaft 14, power driven by pulley 16, are a number of guide sheaves 18 adapted to receive and guide into the tank a number of ends 20 of material in the form, for example, of rovings of glass, rayon or nylon or other continuous filaments, but which also desirably are made up of staple lengths of such materials or of vegetable or animal fibers such as sisal, cotton, wool or the like. These ends are guided downwardly into the tank through the adhesive 12 by means of guide rolls 22 and 24 suitably supported on shafts 26, 28 journaled in the side walls of tank 10. After remaining in the tank long enough to be impregnated with adhesive 12., the duration of immersion being governed by the length of the tank and the speed of travel of the fiber ends, the fiber ends are withdrawn around squeeze rolls 30, 32, which squeeze out the excess, after which the adhesive impregnated string is wound up to form the packages 34.

The adhesive 12 is of a sort which-will adequately impregnate the fiber ends 20 so that in the event that they are made of staple lengths, the string holds together in one continuous length and the adhesive also preferably has the property of remaining tacky or viscid over long periods of time under normal atmospheric conditions.

In use, a package may be secured together using the tying string of my invention, in the manner suggested by Fig. 2. After the string, which is designated at 59, has been wrapped about the box 52, the joining ends 54 and 56 may be merely wrapped around each other and held by their inherent tackiness.

Where the adhesive 12 is to be of the pressure-sensitive type, it may consist of a water soluble body such as animal glue, dextrin, water soluble starch, water soluble casein, etc., which has been plasticized with polyhydric alcohols of Water soluble, high-boiling-temperature character which will not evaporate at ordinary temperatures, such as glycerin, ethylene glycol, molasses, etc. A typical pressure-sensitive adhesive of this type may have the following formula:

Lbs. Glue (dry) 250 Water 250 Glycerin 750 Granulated sugar 187 Other well known substituted.

A second desirable type of pressure-sensitive adhesive is one which is water insoluble. The following is a typical example:

pressure-sensitive adhesives may be Parts Nitrocellulose 35 Diglycol abietate 45 Dibutyl phthalate 25 1 3 for string-like flexibility without permanent tackiness, may be used.

In securing a package with a string impregnated with a solvent plastic adhesive the ends of the string may be moistened with the solvent, water or an organic solvent, and allowed to dry in contact with each other, with or without twisting, but preferably without knotting. Alternatively lengths of the string may be wetted and secured to the package surface without twisting the string ends.

A typical thermoplastic adhesive consists of a thermoplastic resinous body such as chlorinated rubber or polyvinyl chloride suitably plasticized with a high boiling but non-volatile plasticizer. The thermoplastic resinous body is first dissolved in a solvent along with the plasticizer to form a liquid coating composition which is used to impregnate the fibers. The solvent is then evaporated to leave a dry flexible residue of thermoplastic adhesive evenly distributed throughout the fibers. In use, the string may be secured by application of sufiicient heat to soften the thermoplastic and develop its tackiness, after which or simultaneously therewith, the ends may be pressed together and then allowed to cool.

As an example of a preferred embodiment of my invention in which continuous glass filaments are formed into a self-sustaining string by the use of a pressure-sensitive type adhesive, glass fiber filaments are assembled, 20 strands of 150-1/0 per string, and passed through the hot composition described above comprising the water insoluble pressure-sensitive adhesive. The strands are passed through the liquid while it is hot and the excess liquid is then squeezed out. The filaments thus impregnated are allowed to cool to room temperature so that the adhesive sets to a tough, gummy, strong-bonding and highly tacky form. The impregnated string thus produced has high tensile strength and may be secured about the package adhesively and without knotting.

The shape of the string delivered by the squeeze rolls 30, 32 is ribbon-like, being flattened in cross section which, for many uses, is better than ordinary strings which of necessity are round or generally circular in cross section as the result of the spinning in their manufacture. A string made according to the present invention may, however, have a cross section which is circular, if desired, by drawing it through a circular forming die or orifice either after leaving the squeeze rolls or preferably in substitute for those rolls as the die can also function to eliminate the excess adhesive. By suitably shaping the die, the cross section of the string may take on virtually any desired form, either curved or angular. Some variation in shape may be obtained While adhering to the use of rotating squeeze rolls, by suitably shaping the contour of the rolls. The ready moldability of the string of the present invention readily adapts it to such forming operations.

i claim:

A string for securing packages by being wrapped therearound and secured in wrapped position by adhesion, said string consisting of a plurality of fibers bonded together in the form of a single strand by an adhesive, said adhesive being pressure sensitive, the adhesive coating the entire external surface of the strand throughout the length thereof so that the adhesive is available at and adjacent the portions of the string forming the string ends for adhesively securing the string ends against motion in a direction to loosen the string.

References Cited in the file of this patent UNITED STATES PATENTS 787,886 Anet Apr. 25, 1905 1,446,094 Jackson, Feb. 20, 1923 1,529,056 Ellis Mar. 10, 1925 1,856,986 Drew May 3, 1932 2,293,918 Planiol Aug. 25, 1942 2,323,684 Simison July 6, 1943 2,426,257 Ziegler Aug. 26, 1947 2,625,498 Koch Jan. 13, 1953 

